Synchronization of pulse jets



y 1957 L. KUNSAGI SYNCHRONIZATION OF PULSE JETS Filed Sept. 23, 1965 V Ill.

United States Patent O 3,332,236 SYNCHRONIZATION F PULSE JETS Laszio Kunsagi, New York, N.Y., assignor to Foster Wheeler Corporation, Livingston, N.J., a corporation of New York Filed Sept. 23, 1965, Ser. No. 489,660 2 Claims. (Cl. 6039.39)

ABSTRACT OF THE DISCLOSURE In order to synchronize a plurality of pulse jets, a flat disc with slots about its periphery is rotated so that the source of air to each of the pulse jets in the system is passed through the slots in the rotating disc. Preferably, the disc is rotated by a means such as an electric motor, the speed of rotation of which can be readily .controlled.

For some time now increasing interest has been shown in the use of pulse jets for commercial applications. Since pulsating burners have the great drawback that their pressure amplitude and frequency cannot be increased beyond certain levels, a technique had to be found for the manipulation of these variables. By use of a system for synchronizing several clustered burners in such a way that the explosions occur at the same instant, a vast increase in the amplitude component of a sound wave is possible. In an operation where two or more burners operate in a push and pull relationship, synchronization in the predetermined sequence is also possible. Likewise, a combination of these arrangements is possible. Therefore, a need exists for a system by which two or more pulse jets can be accurately synchronized.

Accordingly, it is an object to this invention to provide a system for synchronizing two or more pulse jets which is economical in construction and operation and dependable and durable.

In accordance with this invention, a flat plate-like disk having slots at predetermined equally-spaced locations about its periphery is rotated by a suitable source of rotating motion which includes equipment for controlling the speed of rotation. The source of air to each of the pulse jets in the system is passed through the slots in the rotating disk. In this way, setting the speed of rotation of the disk in accordance with the frequency of the pulse jet, air is permitted to enter each pulsating jet and begin a cycle of combustion within the pulse jet in accordance with the speed of rotation of the disk and the number of the slots in the periphery. This makes it possible to fire two or more jets virtually at the same identical time or to fire them in any desired sequence depending upon the application.

A fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a side cross-sectional view of the invention.

FIGURE 2 is a plan view showing the disk utilized in conjunction with the invention.

Referring now to the drawings and more specifically to FIGURE 1, a top pulse jet burner 21 is located above a lower pulse jet burner 23. Of course, it is understood that any geometric relationship can be used such as side by side or one above the other without in any way changing the spirit of this invention. Where it is desired to synchronize the pulse jets to operate simultaneously the pulse jets are spaced an equal angular distance apart. Where the pulse jets are to operate at different times, the angular relationship is not equal. Surrounding both pulse jets 21, 23 is an insulating sleeve 25. In each burner, an air passageway 27 is formed between the insulating sleeve 25 and the outside of the burner 21. Air enters the space 27 adjacent the discharge end 29 of the two pulse jets 21, 23. This permits the entering air to cool the pulse jets 21, 23. The opposite end 30 of the insulating sleeves 25 is also open to permit the entrance of additional air into the ducts 31. Fuel injectors 33 are utilized in both pulse jets 21, 23. Each fuel injector 33 has a plunger 34 which is depressed to determine the wave length of the ejector 33 to synchronize this wave length with the operation of the pulse jets 21, 23, A suitable fuel for the operation of pulse jets is propane. In the construction of pulse jets, a pipe is utilized which defines a fluid column. In this fluid column, a standing wave pattern is established by means of intermittent pressure pulses created at the closed end of the pipe, these being preferably produced by intermittent combustion of fuel and air charges introduced to the closed end of the pipe. The intermittent combustion is timed to a frequency corresponding preferably to the fundamental frequency of the pipe considered as a quarter-wave organ pipe. In accordance with quarter-wave organ pipe theory, the intermittent pressure pulses so produced serve to resonate the fluid column, creating a pressure antinode (zone of maximum pressure variation and minimum fluid particle velocity variation) adjacent the closed end of the pipe, and a velocity antinode (zone of maximum fluid particle velocity variation and minimum pressure variation) adjacent the discharge orifice at the other end of the pipe.

Air enters an end 35 of each pulse jet 21, 23'opposite the discharge end 29. The burner ends 35 are connected to air tubes 36. The air tubes 36 extend from the burner ends 35 into a block of material in the form of a stationary circular disk 37. The circular disk 37 has a flat face surface 38. In close sliding contact with the flat face 38, but independent thereof, is a flat circular rotatable plate 39. As best seen in FIGURE 2, the rotatable disk 39 has a series of six evenly-spaced notches 41 about its periphery. The notches 41 extend radially inward from the periphery and are located 60 degrees apart about the periphery. As can be seen in FIGURE 1', the air ducts 31 bend around to discharge toward the face of the rotatable disk 39 away from the face 38 of the slab 37 with their ends located to discharge in the path of the rotating notches 41. An annular flange 42 located about the pe riphery of the stationary disk 37 helps prevent leakage where the air ducts 31 meet the rotating disk 39. Air passes through the annular flange 42 by means of apertures 43. On the opposite side of the rotatable disk 39 the ends of the tubes 36 are located in line with the ends of air ducts 31. As the valve 39 rotates, it permits air flow from the air ducts 31 to the air tubes 36 whenever a notch 41 reaches the ends of the ducts 31 and tubes 36. In this way, every sixty degrees of rotation on a six notch wheel would permit air flow into the pulse jets 21, 23 if symmetrically arranged degrees apart. The frequency with which the air would enter would depend upon the speed of rotation of the disk 39 and the amount of air entering would depend not only on the speed of the rotation but the size of the notch 41.

The disk 49 is mounted on a shaft 53 having a coupling 55 and a hub 57 to secure the shaft 53 to the wheel 49. The shaft 53 extends through the stationary disk 37 and into a journal 58 for support. The opposite end of the shaft 53 is secured to a source of rotary motion such as a direct-current electric motor 59. Controlled speed of the direct-current electric motor 59 can be readily achieved by means of rheostats 61 connected within the source (not shown) of direct current supplied to the motor 59. Therefore, by supplying air at a frequency equal to the natural frequency of the pulse jets and setting the speed of rotation of disk 39 in accordance with the frequency of the pulse jets, synchronization is achieved. By varying the location of the pulse jet about the periphery of the circle, it can be seen that the burners can be synchronized to operate either intermittently or simultaneously with a great degree of accuracy and dependability. For example, with the two burners 21, 23 each 180 apart, the burners 21, 23 will fire simultaneously with a six-notch wheel. By placing one burner, 30 out of phase, they will fire alternately.

It is to be understood that the above described embodiment is simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of this invention and forward in the spirit and scope thereof.

What is claimed is:

1. A system for synchronizing a plurality of pulse jets comprising:

a plurality of pulse jets each having an air entrance means and exhaust exit means, the longitudinal axis of the pulse jets being substantially parallel, said air entrance means including a conduit extending along the longitudinal axis from one end of each pulse jet;

a plurality of containers each located substantially concentrically about a separate pulse jet, said containers being open at both ends, one open end being adjacent said exhaust means and the other open end being adjacent said air entrance means, each container having an air opening adjacent said air entrance means;

a stationary circular disk lying in a plane at substantially right angles to the longitudinal axis of said plurality of pulse jets, said stationary circular disk having a side surface adjacent said plurality of pulse jets and a side surface removed from said plurality of pulse jets, said conduit extending through said stationary circular disk from the side adjacent said plurality of pulse jets to the surface removed from said plurality of pulse jets, each air conduit being approximately the same radial distance from the centerpoint of the stationary circular disk;

a flat annular ring, slightly spaced from the side surface of the stationary circular disk removed from said plurality of pulse jets, said fiat annular ring having openings therethrough adjacent said conduits;

duct means connecting said air opening adjacent said air entrance means with the openings in said flat annular ring;

a rotatable circular disk with notches radially located about its periphery, said rotatable circular disk being in sliding relationship with the side surface of said stationary circular disk removed from said plurality of pulse jets and concentrically located with said stationary circular disk, the centerpoint of the rotatable circular disk being common with the centerpoint of the stationary circular disk and the notches being located a substantially equal distance radial distance from the centerpoint of the rotatable circular disk as the conduits are from the centerpoint of the stationary circular disk;

an electric motor connected to the centerpoint of said rotating circular disk; and

means for controlling the speed of rotation of said electric motor.

2. A system for synchronizing a plurality of pulse jets according to claim 1 wherein said conduits are angularly evenly distributed about said stationary circular disk and said notches are of substantially the same dimensions and shape and are angularly evenly distributed about said rotatable circular disk.

References Cited UNITED STATES PATENTS 1,552,272 9/1925 Carner 39.39

2,515,644 7/1950 Goddard 6039.39

2,795,104 6/1957 Zinner 60247 2,928,242 3/1960 Guenther 6039.39

2,930,196 3/1960 Hertzberg 6039.39 2,937,500 5/1960 Bodine 60247 MARK NEWMAN, Primary Examiner.

D. HART, Assistant Examiner. 

1. A SYSTEM FOR SYNCHRONIZING A PLURALITY OF PULSE JETS COMPRISING: A PLURALITY OF PULSE JETS EACH HAVING AN AIR ENTRANCE MEANS AND EXHAUST EXIT MEANS, THE LONGITUDINAL AXIS OF THE PULSE JETS BEING SUBSTANTIALLY PARALLEL, SAID AIR ENTRANCE MEANS INCLUDING A CONDUIT EXTENDING ALONG THE LONGITUDINAL AXIS FROM ONE END OF EACH PULSE JET; A PLURALITY OF CONTAINERS EACH LOCATED SUBSTANTIALLY CONCENTRICALLY ABOUT A SEPARATE PULSE JET, SAID CONTAINERS BEING OPEN AT BOTH ENDS, ONE OPEN END BEING ADJACENT SAID EXHAUST MEANS AND THE OTHER OPEN END BEING ADJACENT SAID AIR ENTRANCE MEANS, EACH CONTAINER HAVING AN AIR OPENING ADJACENT SAID AIR ENTRANCE MEANS; A STATIONARY CIRCULAR DISK LYING IN A PLANE AT SUBSTANTIALLY RIGHT ANGLES TO THE LONGITUDINAL AXIS OF SAID PLURALITY OF PULSE JETS, SAID STATIONARY CIRCULAR DISK HAVING A SIDE SURFACE ADJACENT SAID PLURALITY OF PULSE JETS AND A SIDE SURFACE REMOVED FROM SAID PLURALITY OF PULSE JETS, SAID CONDUIT EXTENDING THROUGH SAID STATIONARY CIRCULAR DISK FROM THE SIDE ADJACENT SAID PLURALITY OF PULSE JETS TO THE SURFACE REMOVED FROM SAID PLURALITY OF PULSE JETS, EACH AIR CONDUIT BEING APPROXIMATELY THE SAME RADIAL DISTANCE FROM THE CENTERPOINT OF THE STATIONARY CIRCULAR DISK; A FLAT ANNULAR RING, SLIGHTLY SPACED FROM THE SIDE SURFACE OF THE STATIONARY CIRCULAR DISK REMOVED FROM SAID PLURALITY OF PULSE JETS, SAID FLAT ANNULAR RING HAVING OPENIKNGS THERETHROUGH ADJACENT SAID CONDUITS; 